The present invention relates to heat-aging resistant polyamide molding materials based on partially crystalline, partially aromatic polyamides as well as to moldings manufactured therefrom.
Thermoplastic polyamides are frequently used in the form of glass-fiber reinforced molding materials as construction materials for components which are exposed to elevated temperatures during their service lives, with thermo-oxidative damage arising. The occurrence of thermo-oxidative damage can admittedly be delayed by the addition of known heat stabilizers, but cannot be permanently prevented, which is expressed e.g. in a drop in the mechanical parameters.
In addition to the heat-aging resistance, the temperatures in use which are caused by the melting points and the glass transition temperatures also play an important role in practice for the use of these polyamide molding materials.
US 2009/0127740 A1 describes a method of manufacturing a component comprising at least two parts which are bonded to one another, with at least one part being formed from a blend of partially aromatic polyamide and aliphatic polyamide. In this respect, in the most preferred variant, 65 to 95% by weight of partially aromatic polyamide (A) is mixed with 5 to 35% by weight of aliphatic polyamide (B) to improve the adhesion of parts which are molded thermoplastically on one another and are manufactured based on partially aromatic polyamide molding materials. The purely aliphatic polyamide (B) is always a component of the molding materials; and the teaching advises against blends of partially aromatic molding materials. No reports have been made on good heat stability or elevated melting points and glass transition temperatures of these molding materials.
To improve the processing capability of partially aromatic polyamides of the PA9T type, US2003/0023008 A1 proposes admixing specific aliphatic polyamides having a carbon/amide ratio of 7 to 12 in a concentration of 10 to 50% by weight. The glass temperature and the crystallization temperature of PA9T should be able to be lowered considerably by this measure while maintaining the melting temperature so that lower mold temperatures and a conventional heating of the injection molds are made possible.